Power, speed and versatility—those are the buzzwords for the crop of concept cars auto makers are using to whet consumer's appetites at the Detroit auto show this week.

There's a small gaggle of prototype sports cars to appeal to youthful speed enthusiasts—or more likely, older drivers craving a family-car replacement. Coupes are back, in various forms including a small, prototype sport-utility vehicle. Judging from the number of Detroit show cars featuring ski racks or outdoorsy images, Americans are a nation of weekend X-Gamers.

Auto makers use concept cars to test consumer reaction to new ideas or styling. One lasting result of the industry's recent crisis is that more show cars aren't fanciful.

Which cars should they build—and which should they bag? Vote at WSJ.com/Autos.

Toyota FT-1

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The Toyota FT-1 concept car.
Agence France-Presse/Getty Images

The FT-1 concept is everything a Camry isn't. Inspired by past ToyotaTM0.90% sports cars, including the Supra, 2000GT and the Scion FR-S, Toyota designers have imagined what a more expensive, impractical Toyota might look like. Among the exotic touches: seats that are ultralight because they have padding only where the driver's backside touches the cushion.

Build It: Why wouldn't Toyota want such a car on its showroom floors to wake up Corolla shoppers?

Bag It: The FT-1 is a looker, but it's no Generation Y magnet. It's a 55-year-old-guy-who-doesn't-want-to spend-on-a-Porsche magnet.

VW Beetle Dune Concept

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The VW Beetle Dune Concept.
Volkswagen of America

Does America want to see what the love child of a VW Beetle and a Jeep would look like? German auto maker Volkswagen AG says yes, and offers the Dune concept. The Dune is based on a 210-horsepower Beetle R-Line model, but is longer, wider and taller. VW says the car has a ski rack built into the roof and rear spoilers.

Build It: VW had a lousy 2013 in the U.S. in part because its lineup lacks versatile SUVs. The Dune could appeal to young singles or couples who don't want a bulky SUV.

Volvo Concept XC Coupé

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The second of Volvo's three concept cars is the new Volvo Concept XC Coupé.
Volvo

Should the iconic Volvo wagon morph into a small SUV with two doors? Volvo Cars, is trying for a resurgence in the U.S., while vying with its rivals to connect with a younger audience. Volvo's boxy station wagons had a dedicated following among baby boomers, but the Concept XC Coupé suggests the brand is anxious about whether 20- and 30-somethings want something different. The XC Coupé is that. It offers just two doors and four seats, and styling Volvo says was inspired by the extreme vibe of POC, a Swedish sporting gear company. Volvo design chief Thomas Ingenlath says the most important aspect of the concept are the proportions, including the long hood.

Build It: Offering a small vehicle for sporty, affluent people who don't have kids to haul around would help Volvo chase away its image as a dowdy car for bourgeois moms and dads.

Bag It: The XC Coupé, with its understated design, risks getting lost in a crowd of luxury small SUVs.

Mini John Cooper Works Concept

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The MINI John Cooper Works Concept
MINI

The revival of BMW AG's Mini has been a success, establishing that a very small car with a distinctive design and smart market positioning could succeed in the U.S. But that success could become a strait jacket. Change too little, and the brand could get stale. Change too much and the Mini becomes just another subcompact dutifully boosting the parent company's fuel-economy scores. The John Cooper Works concept reflects BMW's strategy to start evolving the Mini's different looks without alarming loyalists. The John Cooper Works concept is derived from the new Mini architecture, which affords 30% more cargo space and more room for the occupants.

Build It: Of course they will.

Bag It: The John Cooper Works concept is cool, but it highlights how merely evolutionary the new generation Mini's looks are overall.

Infiniti Q50 Eau Rouge

Starting with a Q50 sedan, which starts at about $35,000, the Eau Rouge concept car from Nissan Motor's Infiniti adds carbon fiber body decorations—an air splitter in the front, casings for the mirrors and a carbon-fiber roof. The concept car is wider and rides lower than the production sedan. The Eau Rouge's racing outfit was styled by Infiniti designers working with the Infiniti Red Bull Racing Formula 1 team.

Build It: A hot rod linked to a brand with strong connections to Gen Y is just what Infiniti needs to get a second look from customers headed toward a BMW M3 performance sedan or a Mercedes AMG model.

Bag It: The red paint job and the carbon-fiber jewelry are nice, but to take buyers from the M3 and AMG, Infiniti will need a screaming engine.

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